Figure 1.

Stick representation of alanyl dipeptide mimetics. Atom types are color-coded: carbon = pink, nitrogen = blue, oxygen = red, hydrogen = white. A: The backbone dihedral angles φ and ψ and the bond angle τ are indicated. B: τ = 105°, φ = −90°, ψ = 0° (i.e., bridge region values of φ and ψ). Blue-shaded spheres indicate steric overlap between main-chain nitrogens for this value of τ. C: τ = 115°, φ = −90°, ψ = 0° (i.e., bridge region values of φ and ψ). Blue-shaded spheres indicate no steric overlap between main-chain nitrogens for this value of τ. [Color figure can be viewed in the online issue, which is available at wileyonlinelibrary.com.]